1. Field of the Invention
The present invention relates to a manufacturing method and a manufacturing apparatus of different color pellets, which can manufacture pellets with thermoplastic resin materials of different colors.
2. Related Art
Conventionally, when pellets of a thermoplastic resin material were manufactured, pellets were manufactured by means of a pellet manufacturing apparatus having a screw type kneading extruder for plasticizing the thermoplastic resin material, a strand die disposed at the front end of the screw type kneading extruder, and a cutting device for cutting strands extruded from said strand die into small pieces while cooling the strands, in such a manner that the thermoplastic resin material was plasticized and extruded from the strand die in the form of strands by the screw type kneading extruder, and then, cut into small pieces by means of the cutting device while being air-cooled or water-cooled.
However, in the conventional technique, when so-called color change was performed to manufacture pellets of a thermoplastic resin material of a color different from the color treated previously, it was necessary to suspend the operation of the pellet manufacturing apparatus so as to perform cleaning for eliminating a thermoplastic resin material of the color which was treated previously and left over in the screw type kneading extruder, the strand die, a screen changer and the cutting device, respectively. In this operation of cleaning, the thermoplastic resin material of the color which was treated previously and left over in the screw type kneading extruder could be eliminated in a comparatively short time, but the thermoplastic resin material of the color treated previously and left over in the strand die, the screen changer, the cutting means and so on except the screw type kneading extruder had to be eliminated in the condition that those parts were removed from the screw type kneading extruder so as to be decomposed. Therefore, there was a problem that it took a long time for the cleaning, and in the meantime, it was necessary to suspend the manufacturing of pellets for a long time.